ofi/common: fix code that broke sessions #12870
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With sessions initialization model (section 11.3 of MPI 4 standard) MPI may be initialized and finalized any number of times. This patch refactors code that was assuming a one shot init/finalize sequence for initializing Open MPI and its MCA param space The underlying problem with the replaced code was that when an app calls MPI_Session_finalize and there are no more sessions active, the MCA param space is destroyed. So if one does not build Open MPI to use dynamically load components, and a component is using static variables in a way that assumes the MCA param space is always preserved if a static variable is set to some value, then things break if a subsequent MPI_Session_init is invoked. Related to open-mpi#12869 Signed-off-by: Howard Pritchard <hppritcha@gmail.com>
hppritcha force-pushed the fix_common_ofi_for_sessions branch from a9a334d to 2f4ba1b Compare hppritcha requested review from a team, cpshereda, edgargabriel and jsquyres and removed request for a team, cpshereda and jsquyres 
edgargabriel approved these changes Oct 23, 2024
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| if (0 > accelerator_rank_index) { | ||
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| param = mca_base_var_find("opal", "opal_common", "ofi", "accelerator_rank"); |
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I think this looks good, there is a case that could be made that this should not be an ofi parameter, but an mca parameter of the accelerator framework (for a later PR)
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Ah good point. I was just keeping things the way they were. I've no objection to moving it in the end to accel framework.
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With sessions initialization model (section 11.3 of MPI 4 standard) MPI may be initialized and finalized any number of times.
This patch refactors code that was assuming a one shot init/finalize sequence for initializing Open MPI and its MCA param space
The underlying problem with the replaced code was that when an app calls MPI_Session_finalize and there are no more sessions active, the MCA param space is destroyed. So if one does not build Open MPI to use dynamically load components, and a component is using static variables in a way that assumes the MCA param space is always preserved if a static variable is set to some value, then things break if a subsequent MPI_Session_init is invoked.
Related to #12869